Color television



May 11, 1954 A. c. scHRoEDE'R l COLOR TELEVISION 2 Smeets-sheet 1 Filed sept. 24, 1949 May ll, 1954 A. C. SCHROEDER COLOR TELEVISION Filed sept. 24, 1949 2 Sheets-Sheet 2 Patented May 11, 1954 UNITED STATES PATENT OFFICE COLOR TELEVISION Alfred C. Schroeder, Feasterville, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application September 24, 1949, Serial No. 117,593

9 Claims. (Cl. 178--69.5)

ponent color or corresponding to the desired component color instantaneously being represented at the transmitter. The process is then repeated for the next selected color component and so Images in their natural color may be trans- 5 on. The processes are repeated rapidly enough mitted over electrical circuits by analyzing the that the several component colors appear simullight from the object being televised not only taneously to the human eye. A typical eld seinto its image elements, but by also analyzing quential color television system is shown and the light of the object into selected primary or described in an article entitled, An experimental component colors and developing therefrom an color television system, beginning on page 141, electrical signal train. 'I'he image may then be RCA Review for June 1946. presently reproduced in its natural color at a re- Although color images have been successfully mote location by appropriately demodulating the reproduced by the aforesaid sequential method, signal train and constructing acolor image therethere are certain fundamental difficulties infrom. volved which tend to reduce the entertainment The basic law that a single electrical-transmisvalue of the eld sequential system. One serious sion circuit can carry but one item of informadiiculty involved includes color action fringes tion at a time is of course as true for the transresulting from movement between individual mission of color images as it is true for the transcomponent color scannings because of the great miSSiOn 0f black and White imageS- F01' eXam- 20 amount of time required for the scanning of a ple, if several electrical signals representative of complete eld. several different selected component colors and It becomes apparent that this diiiculty for the eOVeriIlg the Same frequency band are applied eld sequential method of color image transmis-` SimuliarleOuSly '60 a Single circuit, the correspondsion is eliminated if the rate of change between ing Current impulSeS 105e their Separate identi- 25 the selected color components is made rapidly iieS in the Single Circuit and Carmel? be Separated enough to overcome any indication of movement at the receiving end 0f the Circuit- COIiSequerl'ly, between the different selected component color such information must be conveyed sequentially representations.

Or in Single file, urlleSS Separate eireuii'fS are DIO- If, for exampleJ elemental sequential rate is vided for each of the selected component color employed, that is, if each small image area or repreSerltai'liVe SignalS 1 image element is divided into three separate com- Heretofore, the most popular sequential methponent colors and for each semental area of the Od haS been What iS Gemmenly Called the field image there is transmitted sequentially three dif- Sequential meilledferent color representations, each of whose mag-- In the transmission 0f C0101' images by the eld 35 nitude or energy depends upon the selected com Sequential method, a Single pick-up tube Such aS, ponent colors of the image element, no diiiiculty fer eXample, the SO-ealled image Ori'fhcon is eX- will be experienced with color action fringes. posed in succession to images giving color separa- It at Once becomes apparent, however, that tion corresponding to the various selected com- Such a, method and arrangement would require ponent colors. During the period the camera 40 not only acurate Synchronism in the scanning tulee iS GXPOSed t0 each Component c0101 image, raster, but it would require also an accurate synthe mOSiaC iS concurrently Scanned t0 enable the chronism or speed control in each traverse of the transmission of signals representing the corre- Scanning element in order that Corresponding Spending C0101 Separation image- The Proper color representation at both the transmitter and C0101 Sepalaiien images may be Supplied i0 the 45 receiver would be scanned in perfect synchroimage piek-up tube sequentially by a mechanical nism. arrangement of the rotating lters. The color It has been proposed in this connection to proseparation may also be obtained by electronic vide a sampling oscillator or other signal genswitching of several diierently color sensitive erating device having a frequency much greater image pick-up tubes in sequence. than the horizontal scanning frequency. The

In the conventional field sequential multi-color television receiver a kinescope, or other image producing tube is employed to recreate a black and white image likeness which is viewed or projected through a color filter of the selected comoscillator at the receiver is synchronized With the oscillator at the transmitter by utilizing the standard horizontal synchronizing pulses to control the phase of the sampling oscillator. The output signal of this controlled oscillator is employed to sequentially switch at an elemental sequential rate the several dii-ferent component color cathode ray beam tubes or other selected component color image devices in phase and in synchronism at the transmitter end receiver.

Such an arrangement is well shown and described in the copending U. S. application of John Evans, Serial No. 111,384, entitled Color Television, iiled August 20, 1949.

Y It has been discovered that improved detail and less flicker may be obtained with the dot multiplex or elemental sequential arrangement by employing what is called horizontal interlace. Horizontal interlace refers to `the laying down of different colored dots along the same` line at different positions in successive scans of the same line. Electrically, this is accomplishedv by shifting the phase of the sampling pulses the next time that the same line is scanned so that the dots are then laid down between the dots that were laid down in the rst scan.

It will be remembered that While a single line scan lays down a series of green dots, for example, on the screen with space betweendots, this space is completely lled at the same time by red and blue dots, with great overlapping of the dots.

During the rst scanning eld, for example, the odd numbered lines are scanned in order. That is, the three colored dots are laid down in order along line one. Next, line three is scanned with a displacement of 180 degrees for each color. That is, each dot of like color is positioned in a vertical direction between dots of the same color in the preceding scan line. Theremaining odd lines are scanned in order with the color dot pattern referred to immediately above. This scanning of the iirst eld takes place in onesixtieth of a second. During the second field, the even lines are scanned, rst line two with the colors laid down in overlapping dots, then line four and so on. The dot pattern laid down during the third field is displaced in each line 180 degrees from the position of like colors in the previous scanning-of the `same line. During the fourth field, the l even lines are likewise scanned with a 180 degree displacement from the previous scanning of the same line.A Y

Thus the odd lines are scanned during the iirst field, but dots of the same primary color are separated by spaces. The even lines are scanned during the second field, again with spaces between like color dots. vDuring the third held, the odd lines are again scanned but with the color dots displaced so that the spaces are filled. The even lines are scanned during the fourth field, with the color dots displaced to fill in the spaces left during the second field scanning. Four scanning fields are required to completely cover the image area, with all spaces lled, with. say, green dots. Simultaneously, however the aria is being covered with red dots and with blue do s. l Y

There are sixty elds per second, so it may be said that there are iifteen complete color images per second. It should be remembered that the effective field rate for large-area flicker is sixty per second, the same as for current black and white receivers. At viewing distances such that the picture'line structure is not resolved, the effectA of small area flicker due to line interlace and horizontal interlace is not visible. n

A system of dot or element interlace has been very well shown and described in the co-pending U. S. application to Randall Ballard, Serial No.

' 4 117,528, entitled System of Color Television, led September 24, 1949.

It will at once become apparent that in order to provide for the dot interlace described imn y mediately above, it is necessary to not only control the sampling oscillator in synchronism with the sampling oscillator at the transmitter, but also it is necessarythatl the phase of the sampling oscillators be changed with each line. Various arrangements have been proposed for controlling vand changing the phase with each line by employment of special arrangements, including the transmission of sampling oscillator control fre- Vquencygor alternate switching arrangements included in the receiving circuit.

According to'this invention, the sampling oscillator in both they receiver and transmitter is controlled for proper timing and change of phase yfrom line to line by changing the relative positions of the trailing edge of alternate horizontal synchronizing pulses in order that the sampling oscillator phase will be correct to establish horiw zontal interlace.

The primary objective of this invention is to provide for improved color television.

Another object of this invention is to provide an economical and reliable arrangement for the Y transmission of synchronizing information relating to phasing of sampling oscillators in the'ele mental or dot multiplexingv type of color television systems.

Still another object of this invention is to conveniently modify the presently standard synchronizing signals to permit the operation of elemental multiplex color television receivers.

Still another object of the Yinvention is to so modify the presently standard synchronizing pulses that they will be satisfactory for both the present black and white television receivers as well as the elemental multiplex color television receivers.

Other and incidental objects of the invention will vbecome apparent to one skilled in the art upon a readingof the following specication considered in connection with the accompanying drawings in which:

Figure 1 illustrates-by blockfdiagram a syn chronizing signal generator in which the present invention is employed to provide for proper tim ing of a sampling oscillator in an elemental multiplex color television system.

Figure 2 illustrates graphically a, synchronizing signal train suitable for employment in the transmission of horizontal interlace type color television signals.

Figure 3 shows bycircuit diagram, details of one form of the present invention.

Turning now in more detail to Figure 1 there has been selected a basic type of synchronizing signalgenerator for the provision of the necessary timin'g and 'waveforrris for furnishing scanning beam deiiection information.

The control of the scanning beam in its horizontal and vertical deflection directions has been very adequately covered in prior publications relating to television. It is not intended at thisA time, therefore, to explain in vdetail the various arrangements for producing synchronization at both the transmitter and receiver. It is important, however, for a'proper understanding of the present invention that the operation of a typical synchronizing signal generator be brieiiy described.

Although it is no*u intended that the present invention should be limited to -a synchronizing signal generator of any particular form, there has been selected, for the purpose of illustration and explanation of the operation of this invention, a synchronizing signal generator of a type used in present day television stations.

The synchronizing signal generator illustrated in Figure 1 takes the form of a synchronizing generator such as shown and described in detail in the United States patent to Alda V. Bedford, No. 2,258,943, patented August 14, 1941.

For the convenience in the understanding of the present invention, the modification to the synchronizing signal generator referred to is set out in heavier lines in the drawing of Figure 1 and may be found in the lower left hand corner of the gure.

The desired whole number plus one-half relation between the scanning line frequency and the frame frequency is obtained by utilizing a main or master oscillator I operating at double the line frequency. In this particular case the double line frequency of 31,500 cycles per second is divided by two by means of a frequency divider 2 in order to produce the horizontal deiiecting or line scanning frequency of 15,750 cycles per second and by dividing the double frequency by odd numbers by means of frequency dividers 3, 4 and 5 to produce the vertical defiecting or frame frequency of 60 cycles per second. This method of obtaining the synchronizing impulses for interlaced scanning is described in British Patent 434,469, issued September 2, 1935.

Since the oscillator I is a sine wave oscillator its output is passed through a limiter or clipper circuit 1 for the purpose of producing rectangular impulses, these impulses being impressed upon `the frequency dividers.

The main oscillator I from which the horizontal and vertical synchronizing impulses are derived is locked in with the 60 cycle power line by means of a suitable lock-in circuit indicated by block S to which is supplied 60 cycle impulses from frequency divider Gi and sine wave voltage from the 6() cycle power line, the sine wave voltage passing through a phase shifter 9 determines the phase relation of the synchronizing impulses with respect to the power line supply if desired.

The generator of Figure 1 produces five sepa rate signals as follows:

First, and of the most interest, the scanning synchronizing signal which is to be transmitted to the receiver, second, the blanking signals which are to be transmitted to the receiver along with the picture signals and the synchronizing signals, third, the horizontal synchronizing or driving impulses for the transmitter pick-up tube, fourth, the vertical synchronizing' or driving impulses for the transmitter pick-up tube and fifth, the transmitter tube blanking impulses.

The present invention relates primarily to the production of the synchronizing signals which are transmitted to the receiver.

The one-half line width or double frequency impulses provided by oscillator I andlimiter circuit l are the basic signals upon which the whole synchronizing signal train is built. More specifically the front edges of the 31,500 cycle per second impulses corresponds to the front edges of all the impulses comprising the nal composite synchronizing signal shown in Figure 2.

The 31,5010y cycle per second impulses are obtained by taking impulses from the limiter circuit i, delaying them a suitable amount by a delay network D to make the front edges of the impulses start at the proper time, impressing them upon a multivibrator II which may be adjusted to make the impulses of the proper width, passing the resulting impulses through a limiter or clipping circuit I2 which supplies the final impulses to a mixing portion of the circuit indicated at I3.

Circuit details which are not important to the present invention will be omitted in the interest of clarity. Circuit details may be obtained by reference to the aforementioned Bedford Patent 2,258,943.

Certain portions of the double line frequency impulses are not desired. rIhe blanking of the undesired pulses is obtained by taking impulses from a 15,750 cycle per second multivibrator I6 which feeds into limiter-mixer circuit Il. To eliminate the impulses obtained from the multivibrator I5 for the period during which the double frequency impulses are desired, 60` cycle impulses are also fed into the limiter-mixer Il, the 60 cycle impulses being taken from a multivibrator I8 through a limiter circuit I9.

Certain pulses must be of double width. Such double width pulses are obtained by taking 15,- 750 cycle pel` second impulses from multivibrator 22 which is driven by the frequency divider' 2 through a delay circuit D, the delay circuit determining the time the front edges of the impulses start and the adjustment of multivibrator 22 determining the width of the impulses. The 15,750A cycle per second impulses from multivibrator 22 are fed into a limiter-mixer circuit 23 together with the 60 cycleimpulses. The desired signal appears in the output of limiter 25 following the mixer 23.

In accordance with the present invention alternate horizontal pulses must have a delayed trailing edge. Accomplishment of this includes dividing the 15,750 cycle per second signal of frequency divider 2, by two in frequency divider 25. The output signal of frequency divider 25 is a square wave having a frequency of 7,875 cycles per second. This 7,875 cycle per second signal is employed to control the width of the pulses generated by multivibrator 22. That is, alternate pulses produced by multivibrator 22 are made longer in time duration. The circuit details are shown in Figure 3.

By mixing the sixty cycle impulses derived from a multivibrator 2B and the 31,500 cycle impulses taken from the limiter 7, a series of impulses may be. obtained to produce the slotted vertical synchronizing impulses.

Multivibrator 2S is adjusted to control the start of the slotted impulses by producing impulses which have such width that the back edge occurs just before the slotted impulse is to start. The impulses produced by multivibrator 25 are supplied to limiter-mixer 2l, together with 31,500 cycle per second impulses from a multivibrator 3l, whereby a selected 31,500 cycle impulse is caused to trigger off a 60' cycle signal near the back edge of each impulse produced by multivibrator 2S. In the output circuit of multivibrator 28 there appears the delayed impulses which are fed into a limiter-mixer 29.

There is also fed into the limiter-mixer 23 the 31,500 cycle impulses whose width is determined by multivibrator 3l which is in turn driven through delay circuits D from the limiter i.

Thefinal signal then appears in the output of a limiter 32 following thelimiter-mixer 29.

The video blanking signal is a mixture of 60 cycle impulses produced by a multivibrator 36 and 15,750 cycle impulses produced by a multivibrator 31. The two groups of impulses are supplied to a limiterV mixerV circluit 38, the 60 cycle impulses first passing through a limiter 39. The final signal appears at line amplier GI.

The image pick-up tube horizontal driving impulses are obtained from a multivibratorl d2 through a limiter or clipper tube d3. The final signal appears at line ampliiier 1M.

The image pick-up tube vertical driving irnpulses are obtained from a 60 cycle multivibrator i8 through a limiter circuit d1, the iinal signal appearing in the output circuit of line ampliiier 48.

The image pick-up tube blanking impulses are obtained from a 60 cycle multivibrator 09 and a 15,750 cycle multivibrator I. The outputs of these multivibrators being supplied to a limitermixer circuit 52, and the 60 cycle signal rst passing through limiter 53. The final signal appears in the output circuit of a line amplifier 5d.

Turning now in more detail to Figure 2, there is shown a composite synchronizing signal provided in accordance with this invention. It is important to notice that alternate horizontal synchronizing pulses are wider. The alternate synchronzing pulses have been widened by adding to the trailing edge but not interfering with the leading edge. The dilerence has been emphasized in the drawing in the interest of clarity. The amount added to the trailing edge is governed by the phase displacement of the dots :from one line to the next. It will also be seen that the change in width of alternate pulses is not effective in the signal train during vertical deflection. The continuation of the proper timing from one eld to the next is of course important. This important action is accomplished by the arrangement provided in Figure 3.

Turning now in more detail to Figure 3, there is shown in detail the elements necessary for the practice of this invention in one of its forms.

A multivibrator with two stable states of condition is quite well known to the electrical art and may be employed as a sequence-operated scale-of-two counter circuit. This type of circuit is perhaps the most frequently employed counter circuit because of its reliability and simplicity.

A basic scale-of-two counting circuit is shown by way of example in Figure 3. The pulses to be counted are applied to both sections of tube 81 but only one section can conduct at a time because of the interconnection between sections by resistances BI. Each time a trigger pulse is applied, the conducting and nonconducting sections of tube 81 are interchanged. This action is brought about by applying a negative pulse to the cathode of dual diode tube 85. The circuit is so arranged that the conducting section of the double triode 31 will be cut ofi and regeneration initiated. This results in a rectangular waveform of half the input signal frequency at the plate of either tube. This output may be used directly to control the width of the pulses of multivibrator IIJI.

The multivibrator tube ||l| including two sections of a triode for purposes of illustration, is of the monostable type. It is essentially a twostage resistance-capacitance-coupled amplifier with one tube section cut off and the other normally conducting. In the balanced condition of the circuit the second section of tube IBI is normally in a conducting state. This results from the fact that a negative bias is applied to the iirst section while a positivefbias is applied to the control electrode of the second section. Y

For the purpose of a description of the operation of the circuit involving the multivibrator l0 I let it be assumed that the second section of tube I0! is conducting.

Upon the arrival of a negative pulse at the anode connection of the rst section, a negative pulse is applied to the control electrode of the second section through condenser |03. This negative pulse to the control electrode of the second section of tube |0| causes the second section to stop drawing current and be cut 01T. In accordance with the well known operation of`multii' vibrators, the potential of the anode of the second section then raises to a more positive value, causing the control electrode of the iirst section of tube I0| to also go in a positive direction. This results in a change of the conduction from the second section to the first section. In accordance with the well known operation of multivibrators there is produced in the output circuits a series of pulses which is timed in accordance with the input pulses applied to the anode of the iirst section of tube |l. In normal operation, the pulses in the output of the second section of tube IUI would be of constant width controlled manually by the potentiometer |05.

In accordance with the present invention, however, it is necessary to obtain pulses alternate ones of which are of diierent width. In other words, it is necessary in accordance with the present invention to provide a train of signal pulses alternate ones of which have later trailing edges.

This is accomplished by applying the incoming square wave signal |01, obtained from tube 81, to the biasing resistance |09 in such a manner that it will change the bias applied to the control electrode of the second section or tube |0| on alternate horizontal pulses.

For example, if the condition of bias on the second section of tube |0I is at themore positive portion of the curve |01, the potential of the control electrode of the secondsection of the tube |0| Will more quickly reach a value permitting the second section to conduct after it has been turned 01T by the first section. It will be seen that the width of the output pulse of tube 10| will be dependent upon the time it takes for the charge on the condenser |03 to change and permit second section of tube IUI to again conduct.

If, however, the potential applied to the grid resistance |09 by tube 81 is on the negative portion of the curve |01, it will take longer for the charge on the condenser |03 to change back to the state at which the second section of tube |0| will become conductive.

It will therefore be seen that the width of all the pulses may be controlled by adjusting potentiometer |05, while the width of alternate pulses may be controlled by adjusting potentiometer 9 I.

The unmodified horizontal synchronizing pulse applied to the rst section of tube |0| may be obtained from the delay network connected to the frequency dividing circuit, illustrated in Figure 1 by block 2.

The voltage waveform |01 applied to potentiometer |09 is obtained from the frequency dividing circuit involving tube 81 which also is illustrated by block 25 in Figure 1 of the drawing.

The series of modified horizontal synchronizing signals may then be applied to the limiter mixer represented by block 23 of Figure 1. The output voltage curve is illustrated graphically as curve Il l in Figure 3 to be combined in mixer I3 of the synchronizing signal generator illustrated in Figure l.

It is important, however, for the proper operation of the present invention that the modiiied horizontal synchronizing pulses be not only employed in the synchronizing signal generator for transmission to the receiver, but the same modiiied horizontal synchronizing pulses be employed in the transmitter circuit for synchronizing the sampling devices at the transmitter in accordance with the overall procedure outlined in the co-pending applications of John Evans and Randall Ballard, referred to above.

In this particular form of the invention the modied horizontal synchronizing signal as illustrated by curve ill is differentiated in a condenser resistance circuit involving condenser l i3 and resistance H5. Tube Hl is given a positive bias on the control electrode and functions as a clipper and an inverter circuit. The output signal of tube ill is illustrated graphically by curve H9.

It is important to notice that the front edges of the pulses of curve l it correspond to the trailing edge of the pulses in curve l Il. It is also important to notice that the width of the pulses in curve H9 are constant, while their spacing is irregular. The amount of difference in spacing is chosen in order to properly interlace the sampling times in accordance with the proposals outlined in detail in the aforementioned Ballard application. This amount of time may, for example, amount to half of the time between one color sampling in order to provide for the proper horizontal interlace. The signal taking the form of the pulses having irregular spacing but constant Width, is applied to the control electrode of tube i2! whose plate is connected to a positive potential, and whose cathode is connected to coil E23 which is the tank coil of the ringing circuit involving coil 23 and condenser E25.

in accordance with the teachings of Ballard and Evans whose co-pending applications are referred to above, the pulsed oscillator or ringing circuit must maintain its oscillation of sampling energy at a constant amplitude in order to sample along the Width of an entire luie. This maintenance of oscillation is caused by the regeneration of tube H21 which is adjusted to prevent decay of the oscillations in the ringing circuit.

Means for obtaining three phase output signals from the ringing circuit are connected to the ringing circuit as illustrated by block |23. The several output signals of block l28 are employed for sampling the several selected component colors in time multiplex.

Although the circuit arrangement illustrated is directed primarily for employment in the transmitting station the elements including the differentiator, inverter, clipper pulsed oscillator and means for producing three phase output signals may be employed in the receiver to convert the modied horizontal synchronizing pulses to produce sampling information for the reproduction of images in their natural color.

Having thus described the invention Iwhat is claimed is:

1. A synchronizing system comprising in combination a monostable multivibrator having a synchronizing input circuit and a control terminal, said monostable multivibrator having a pulse duration dependent upon the control voltage applied to said control terminal, a source of pulses of a predetermined frequency, a source of substantially square Iwaves, said square Waves having a frequency one half the frequency of the pulses of said source of pulses, means of applying said pulses to said synchronizing input circuit, and means for applying said square waves to said control terminal.

2. A synchronizing circuit comprising a source of synchronizing pulses, a frequency divider having an input and output circuit, said frequency divider input circuit connected to said source of synchronizing pulses, a monostable multivibrator having a synchronizing input circuit and a control terminal, said monostable multivibrator having a pulse duration dependent upon the control voltage applied to said control terminal, a connection between said source of synchronizing pulses and said synchronizing input circuit, and a connection between said frequency divider output circuit and said control terminal.

3. In a color television synchronizing circuit, a horizontal interlace phasing circuit comprising in combination a monostable multivibrator having a synchronizing input and a control terminal, said monostable multivibrator having a pulse duration dependent upon the control voltage applied to said control terminal, means for applying pulses to said synchronizing input circuit, and means for applying the same potential to said control terminal only during alternate pulses.

Li. In a color television synchronizing circuit, a horizontal interlace phasing circuit comprising in combination a monostable multivibrator having a synchronizing input circuit and a control terminal, said monostable multivibrator having a pulse duration dependent upon the control voltage applied to said control terminal, a source of line dencction synchronizing pulses, a frequency halver to produce a square wave, means for applying said pulses to said synchronizing input circuit, and a connection between said frequency halver and said control terminal.

5. A monostable multivibrator having a synchronizing input circuit and a contro1 terminal, said multivibrator also having an output circuit,

said monostable vibrator having a pulse duration dependent upon the control voltage applied to said control terminal, a diierentiator, said dierentiator connected to said multivibrator output circuit, a source of pulses of a predetermined frequency, a substantially square Wave source, said square Wave source having a frequency one half the frequency of the pulses of said source of pulses, means for applying said pulses tc said synchronizing input circuit, and means for applying said square waves to said contro1 terminal.

6. In a color television synchronizing circuit, a horizontal interlace phasing circuit comprising a multivibrator having a synchronizing input circuit and a control terminal, said multivibrator having a pulse duration dependent upon the control voltage applied to said control terminal, a source of line deflection synchronizing pulses, a source of substantially square waves, said square waves having a frequency one half the frequency of the pulses of said source of pulses, means for applying said pulses to said synchronizing input circuit, and means for applying said square Waves to said control terminal.

7. A synchronizing circuit comprising in combination means for developng horizontal deflection synchronizing pulses, a monostable multiasf/8,351

vibrator havingasynchronizing input circuit and a control terminal, said monostable multivibrator having a pulse duration dependent upon the control voltage applied to said control terminal, means for applying said pulses to said synchronizing'input circuit, and means forvapplying the 'same potential to said control terminal only during alternate pulses.

8. Apparatus for providing color interlace'information comprising in combination synchronizing signal generating means for developing a train of'horizontal synchronizing pulses, means for providing an interlace designating signal and means for inserting said interlace designating signal in said train of horizontal synchronizing pulses immediately following the pulses of said train of' horizontal-synchronizing pulses thereby to provide interlace information.l

9.- Apparatus for providing color interlace information comprising in combination synchronizing signal generating means for developing a train of horizontal synchronizing pulses, means for providing an interlace designating signal, and means for inserting said interlace designating signal in saidtrain ofY horizontal synchronizing pulses immediately following the pulses of said train of horizontal synchronizing pulses, said interlace designating signal particularly characterized in that the interlace designating signal following alternate horizontal pulses are similar and the interlacevdesignating signal following adjacent of said synchronizing pulses are dissimilar.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,258,943 Bedford Oct. 14, 1941 2,363,809 Schade Nov. 28, 1944 20 A 2,546,972 Chatterjea Apr. 3, 1951 

